1. Field of the Invention
The present invention relates to a capacitance-type contact detecting device with which a user can input information by touching the device with a finger or the like and a contact detecting method. The present invention also relates to a display device that has a function of the contact detecting device.
2. Description of the Related Art
A contact detecting device called a touch panel is known. In general, the contact detecting device is a device that detects that a finger of a user, a pen, or the like comes into contact or approaches a detection surface.
On the other hand, the touch panel is formed over a display panel and displays various buttons on a display surface as images to thereby allow, acting as a substitute for normal buttons, a user to input information. Application of this technique to a small mobile apparatus, the arrangement of buttons can be shared with a display. This leads to significant merits such as an increase in size of a screen, space saving for an operation unit, and a reduction in the number of components.
In this way, in general, “touch panel” refers to a panel-like contact detecting device combined with a display device.
However, when the touch panel is provided in a liquid crystal panel, the thickness of an entire liquid crystal module increases.
Therefore, for example, JP-A-2008-9750 discloses a liquid crystal display element with a touch panel in which a conductive film for the touch panel is provided between an observation side substrate of a liquid crystal display element and a sheet polarizer for observation arranged on an outer surface of the observation side substrate and a capacitance-type touch panel having an outer surface of the sheet polarizer as a touch surface is formed between the conductive film for the touch panel and the outer surface of the sheet polarizer. A reduction in thickness of the liquid crystal display element is realized.
The capacitance-type touch sensor includes plural driving electrodes and plural detection electrodes that form capacitors in conjunction with the respective plural driving electrodes.
Sensor detection accuracy is proportional to the number of driving electrodes and the number of detection electrodes. However, if sensor output lines are provided separately from the detection electrodes, an extremely large number of wires are necessary. Therefore, in order to cause the detection electrodes to function as the sensor output lines as well, a driving method for AC-driving one of plural driving electrodes and shifting the AC-driven driving electrode in a direction in which the driving electrodes are arranged at a fixed pitch (hereinafter, scanning direction) is mainly adopted. With the method of performing scanning in one direction of the AD-driven driving electrode, when a potential change in the detection electrode is observed following the scanning, it is possible to detect, from a position during the scanning where the potential change occurs, whether a detection object comes into contact with or approaches a touch panel surface.